Hi experts, This patchset is the implementation for signature verification of hibernate snapshot image. The origin idea is from Jiri Kosina: Let EFI bootloader generate key-pair in UEFI secure boot environment, then pass it to kernel for sign/verify S4 image. Due to there have potential threat from the S4 image hacked, it may causes kernel lost the trust in UEFI secure boot. Hacker attack the S4 snapshot image in swap partition through whatever exploit from another trusted OS, and the exploit may don't need physical access machine. So, this patchset give the ability to kernel for parsing RSA private key from EFI bootloader, then using the private key to generate the signature of S4 snapshot image. Kernel put the signature to snapshot header, and verify the signature when kernel try to recover snapshot image to memory. How To Enable ============== Set CONFIG_SNAPSHOT_VERIFICATION kernel config to enable. And you can also choice which hash algorithm should snapshot be signed with. Then rebuild kernel. This function depends on EFI_STUB. Please note this function need UEFI bootloader's support to generate key-pair in UEFI secure boot environment, e.g. shim. Current shim implementation by Gary Lin: Git: https://github.com/lcp/shim/tree/s4-key-upstream RPM: https://build.opensuse.org/package/show/home:gary_lin:UEFI/shim Please use the shim from above URL if you want to try. Please remember add the hash of shim to db in UEFI BIOS because it didn't sign by Microsoft or any OSV key. The default behavior is taint kernel when signature check fail. If you want direct fail whole hibernate snapshot restore procedure when signature check does not pass, please use snapshot_sig_enforce kernel parameter or CONFIG_EFI_SECURE_BOOT_SNAPSHOT_SIG_ENFORCE config. If you want binding UEF secure boot with sig_enforce flag, then you can use CONFIG_EFI_SECURE_BOOT_SNAPSHOT_SIG_ENFORCE config. The sig_enforce flag will auto enabled when UEFI secure boot enabled. Behavior ========= The RSA key-pair are generated by EFI bootloader(e.g. shim) in UEFI secure boot environment, then put private key to S4SignKey, public key to S4WakeKey EFI variable. Kernel's behavior as following: + First, EFI stub kernel will check the following 2 EFI variable: S4SignKey-fe141863-c070-478e-b8a3-878a5dc9ef21 [BootService] S4WakeKey-fe141863-c070-478e-b8a3-878a5dc9ef21 [Runtime][Volatile] S4SignKey and S4WakeKey is a RSA key-pair: - S4SignKey is a private key that's used to generate signature of S4 snapshot. The blob format of S4SignKey is PKCS#8 _uncompressed_ format, it should packaged a RSA private key that's followed PKCS#1. - S4WakeKey is a public key that's used to verify signature of S4 snapshot. The blob format of S4WakeKey is X.509 format, it should packaged a RSA public key that's followed PKCS#1. + EFI stub kernel will load the S4SignKey blob to RAM before ExitBootServices, then copy to a memory page that's maintained by hibernate_key.c. This private key will be used to sign snapshot when hibernate launched. + When sig_enforce flag set to TRUE, means force check verification pass: - If kernel didn't find S4 key-pair, then kernel will block hibernate functions including kernel space and userspace hibernate. - If snapshot signature check fail when hibernate resume, the snapshot restore procedure will fail and running normal boot process. + When sig_enforce flag set to FALSE, means not force the verification pass: - If kernel didn't find S4 key-pair, then the hibernate function still available. But kernel will be tainted after hibernate resume. - If snapshot signature check fail when hibernate resume, the snapshot restore procedure will allow continue. But kernel will be tainted. On EFI bootloader side, the behavior as following: + EFI bootloader must generate RSA key-pair when: - First time boot, bootloader generate key-pair when didn't find it. - Bootloader need re-generate after found GenS4Key efi variable from OS: GenS4Key-fe141863-c070-478e-b8a3-878a5dc9ef21 [Runtime][Non-Volatile] The size of GenS4Key is 1 byte, OS(kernel or userland tool) will set it to "1" for notify efi bootloader regenerate key-pair. - If re-generate key-pair, bootloader need store the new public key to EFI bootservices variable by itself, e.g. store to NextWakeKey variable When system resumed from hibernate, bootloader need copy public key from NextWakeKey to S4WakeKey, then kernel will use it to verify snapshot image. Implementation ============== Whole implementation including 3 parts: shim, asymmetric keys and hibernate: + shim: Current solution implemented by Gary Lin: https://github.com/lcp/shim/tree/s4-key-upstream Please use shim from the above URL if you want to try. Please remember add this shim to db because it didn't sign by Microsoft or any OSV key. + Asymmetric keys: This patchset implemented uncompressed PKCS#8 and RSA private key parser, it also implement the signature generation operation of RSASSA-PKCS1-v_5 in PKCS#1 spec. [RFC3447 sec 8.2.2] Set CONFIG_PKCS8_PRIVATE_KEY_INFO_PARSER=y will give kernel the abilities to parsing private key in uncompressed PKCS#8 blob and generate signature. + Hibernate: Set CONFIG_SNAPSHOT_VERIFICATION=y will enable the function of snapshot signature generation and verification. I reserved 512 byes size in snapshot header for store the signature that's generated from the digest with SHA algorithms. For adapt S4 signature check to secure boot, It Base on Matthew Garrett's 2 patches in "[PATCH] Add additional security checks when module loading is restricted" series: https://lkml.org/lkml/2013/8/19/331 [PATCH 01/10] Add secure_modules() call [PATCH V3 11/11] Add option to automatically enforce module signatures when in Secure Boot mode Please help review this RFC patchset! Appreciate for any comments! V4: - Cleaned source code, use helper functions to reduce #ifdef chunk. - Introduced sig_enforce flag, taint kernel when signature check fail. - Use forward_info structure to maintain the empty of forward information and new sign key from boot kernel to resume target kernel. - Use efivar API to access S4WakeKey variable. - Call set_key_regen_flag() to set key-pair regeneration flag in hibernate.c and user.c V3: - Load S4 sign key before ExitBootServices in efi stub. - In Makefile, moved hibernate_keys.o before hibernate.o for load S4 sign key before check hibernate image. It makes sure the new sign key will be transfer to resume target kernel. - Set "depends on EFI_STUB" in Kconfig. V2: - Moved SNAPSHOT_VERIFICATION kernel config to earlier patch. - Add dummy functions to simplify the ifdef check. - Sent to opensuse-kernel@xxxxxxxxxxxx for review: http://lists.opensuse.org/opensuse-kernel/2013-08/msg00025.html V1: - Internal review - github: https://github.com/joeyli/linux-s4sign/commits/devel-s4sign Lee, Chun-Yi (15): asymmetric keys: add interface and skeleton for implement signature generation asymmetric keys: implement EMSA_PKCS1-v1_5-ENCODE in rsa asymmetric keys: separate the length checking of octet string from RSA_I2OSP asymmetric keys: implement OS2IP in rsa asymmetric keys: implement RSASP1 asymmetric keys: support parsing PKCS #8 private key information asymmetric keys: explicitly add the leading zero byte to encoded message Hibernate: introduced RSA key-pair to verify signature of snapshot Hibernate: generate and verify signature of snapshot Hibernate: Avoid S4 sign key data included in snapshot image Hibernate: taint kernel when signature check fail Hibernate: show the verification time for monitor performance Hibernate: introduced SNAPSHOT_SIG_HASH config for select hash algorithm Hibernate: notify bootloader regenerate key-pair for snapshot verification Hibernate: adapt to UEFI secure boot with signature check Documentation/kernel-parameters.txt | 7 + arch/x86/Kconfig | 11 + arch/x86/boot/compressed/eboot.c | 92 +++++++ arch/x86/include/asm/efi.h | 9 + arch/x86/include/uapi/asm/bootparam.h | 1 + arch/x86/kernel/setup.c | 7 + arch/x86/platform/efi/efi.c | 68 +++++ crypto/asymmetric_keys/Kconfig | 11 + crypto/asymmetric_keys/Makefile | 16 + crypto/asymmetric_keys/pkcs8.asn1 | 19 ++ crypto/asymmetric_keys/pkcs8_info_parser.c | 152 ++++++++++ crypto/asymmetric_keys/pkcs8_parser.h | 23 ++ crypto/asymmetric_keys/pkcs8_private_key.c | 148 ++++++++++ crypto/asymmetric_keys/pkcs8_rsakey.asn1 | 29 ++ crypto/asymmetric_keys/private_key.h | 29 ++ crypto/asymmetric_keys/public_key.c | 32 +++ crypto/asymmetric_keys/rsa.c | 296 +++++++++++++++++++- crypto/asymmetric_keys/signature.c | 28 ++ include/crypto/public_key.h | 28 ++ include/keys/asymmetric-subtype.h | 6 + include/linux/efi.h | 25 ++ include/linux/kernel.h | 1 + include/linux/suspend.h | 7 + kernel/panic.c | 2 + kernel/power/Kconfig | 77 +++++- kernel/power/Makefile | 1 + kernel/power/hibernate.c | 23 ++- kernel/power/hibernate_keys.c | 410 ++++++++++++++++++++++++++++ kernel/power/main.c | 7 +- kernel/power/power.h | 62 +++++ kernel/power/snapshot.c | 323 ++++++++++++++++++++++- kernel/power/swap.c | 4 + kernel/power/user.c | 14 +- 33 files changed, 1946 insertions(+), 22 deletions(-) create mode 100644 crypto/asymmetric_keys/pkcs8.asn1 create mode 100644 crypto/asymmetric_keys/pkcs8_info_parser.c create mode 100644 crypto/asymmetric_keys/pkcs8_parser.h create mode 100644 crypto/asymmetric_keys/pkcs8_private_key.c create mode 100644 crypto/asymmetric_keys/pkcs8_rsakey.asn1 create mode 100644 crypto/asymmetric_keys/private_key.h create mode 100644 kernel/power/hibernate_keys.c -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html